When you get home with your newborn baby, you will very likely find that in the first couple of weeks they will lose some weight, whether they are breast or bottle fed. This is quite normal and your midwife or health visitor will be able to explain to you how much weight loss is usual and be able to reassure you about your baby.
You will probably have received some new baby gifts of clothes for your baby and if you are lucky will find that you have a selection of soft body suits, bootees and sleepwear. If your baby is small at birth, you will probably find that everything is too big, but once your baby puts back on the lost weight and then starts growing, you will find that the clothes soon fit and then are soon grown out of.
Wise and experienced friends and relatives will have given you some next size up clothes to allow for this and this gives you the pleasure of opening and using the new baby gifts as time goes on, so reminding yourself of the affection and support you have around you.